When creating your personal body of knowledge system a key principle is to reduce any friction that slows down your thinking.
A tool for supporting your PBOK should be extremely easy to get your thoughts recorded and allow you the flexibility to refine them at a later time.
If there are functions you need to remember, and times when you need to wait for the tool to process, that will impede your thinking and your creativity.
For me, Obsidian is the ideal PBOK tool. It allows me to start small and then slowly build the complexity.
In Obsidian you can just start typing and linking things together creates that cow path that you can refine into your superhighway.
Keep this principle of reducing thinking friction when evaluating what PBOK tool will work for you.